1. Field of the Invention
The present invention relates to an apparatus and methods for facilitating the connection of tubulars. More particularly, the invention relates to an interlock system for a top drive and a spider for use in assembling or disassembling tubulars.
2. Background of the Related Art
In the construction and completion of oil or gas wells, a drilling rig is constructed on the earth""s surface to facilitate the insertion and removal of tubular strings into a wellbore. The drilling rig includes a platform and power tools such as an elevator and a spider to engage, assemble, and lower the tubulars into the wellbore. The elevator is suspended above the platform by a draw works that can raise or lower the elevator in relation to the floor of the rig. The spider is mounted in the platform floor. The elevator and spider both have slips that are capable of engaging and releasing a tubular, and are designed to work in tandem. Generally, the spider holds a tubular or tubular string that extends into the wellbore from the platform. The elevator engages a new tubular and aligns it over the tubular being held by the spider. A power tong and a spinner are then used to thread the upper and lower tubulars together. Once the tubulars are joined, the spider disengages the tubular string and the elevator lowers the tubular string through the spider until the elevator and spider are at a predetermined distance from each other. The spider then re-engages the tubular string and the elevator disengages the string and repeats the process. This sequence applies to assembling tubulars for the purpose of drilling, running casing or running wellbore components into the well. The sequence can be reversed to disassemble the tubular string.
During the drilling of a wellbore, a drill string is made up and is then necessarily rotated in order to drill. Historically, a drilling platform includes a rotary table and a gear to turn the table. In operation, the drill string is lowered by an elevator into the rotary table and held in place by a spider. A Kelly is then threaded to the string and the rotary table is rotated, causing the Kelly and the drill string to rotate. After thirty feet or so of drilling, the Kelly and a section of the string are lifted out of the wellbore, and additional drill string is added.
The process of drilling with a Kelly is expensive due to the amount of time required to remove the Kelly, add drill string, reengage the Kelly, and rotate the drill string. In order to address these problems, top drives were developed.
FIG. 1A is a side view of an upper portion of a drilling rig 100 having a top drive 200 and an elevator 120. An upper end of a stack of tubulars 130 is shown on the rig 100. The figure shows the elevator 120 engaged with a tubular 130. The tubular 130 is placed in position below the top drive 200 by the elevator 120 in order for the top drive with its gripping means to engage the tubular.
FIG. 1B is a side view of a drilling rig 100 having a top drive 200, an elevator 120, and a spider 400. The rig 100 is built at the surface 170 of the well. The rig 100 includes a travelling block 110 that is suspended by wires 150 from draw works 105 and holds the top drive 200. The top drive 200 has a gripping means for engaging the inner wall of tubular 130 and a motor 240 to rotate the tubular 130. The motor 240 rotates and threads the tubular 130 into the tubular string 210 extending into the wellbore 180. The motor 240 can also rotate a drill string having a drill bit at an end, or for any other purposes requiring rotational movement of a tubular or a tubular string. Additionally, the top drive 200 is shown with elevator 120 and a railing system 140 coupled thereto. The railing system 140 prevents the top drive 200 from rotational movement during rotation of the tubular string 210, but allows for vertical movement of the top drive under the travelling block 110.
In FIG. 1B, the top drive 200 is shown engaged to tubular 130. The tubular 130 is positioned above the tubular string 210 located therebelow. With the tubular 130 positioned over the tubular string 210, the top drive 200 can lower and thread the tubular into the tubular string. Additionally, the spider 400, disposed in the platform 160, is shown engaged around a tubular string 210 that extends into wellbore 180.
FIG. 2 illustrates a side view of a top drive engaged to a tubular, which has been lowered through a spider. As depicted in the Figure, the elevator 120 and the top drive 200 are connected to the travelling block 110 via a compensator 270. The compensator 270 functions similar to a spring to compensate for vertical movement of the top drive 200 during threading of the tubular 130 to the tubular string 210. In addition to its motor 240, the top drive includes a counter 250 to measure rotation of the tubular 130 during the time tubular 130 is threaded to tubular string 210. The top drive 200 also includes a torque sub 260 to measure the amount of torque placed on the threaded connection between the tubular 130 and the tubular string 210. The counter 250 and the torque sub 260 transmit data about the threaded joint to a controller via data lines (not shown). The controller is preprogrammed with acceptable values for rotation and torque for a particular joint. The controller compares the rotation and the torque data to the stored acceptable values.
FIG. 2 also illustrates a spider 400 disposed in the platform 160. The spider 400 comprises a slip assembly 440, including a set of slips 410, and piston 420. The slips 410 are wedge-shaped and are constructed and arranged to slidably move along a slopped inner wall of the slip assembly 440. The slips 410 are raised or lowered by piston 420. When the slips 410 are in the lowered position, they close around the outer surface of the tubular string 210. The weight of the tubular string 210 and the resulting friction between the tubular string 210 and the slips 410, forces the slips downward and inward, thereby tightening the grip on the tubular string. When the slips 410 are in the raised position as shown, the slips are opened and the tubular string 210 is free to move axially in relation to the slips.
FIG. 3 is cross-sectional view of a top drive 200 and a tubular 130. The top drive 200 includes a gripping means having a cylindrical body 300, a wedge lock assembly 350, and slips 340 with teeth (not shown). The wedge lock assembly 350 and the slips 340 are disposed around the outer surface of the cylindrical body 300. The slips are constructed and arranged to mechanically grip the inside of the tubular 130. The slips 340 are threaded to piston 370 located in a hydraulic cylinder 310. The piston is actuated by pressurized hydraulic fluid injected through fluid ports 320, 330. Additionally, springs 360 are located in the hydraulic cylinder 310 and are shown in a compressed state. When the piston 370 is actuated, the springs decompress and assist the piston in moving the slips 340. The wedge lock assembly 350 is constructed and arranged to force the slips against the inner wall of the tubular 130 and moves with the cylindrical body 300.
In operation, the slips 340, and the wedge lock assembly 350 of top drive 200 are lowered inside tubular 130. Once the slips 340 are in the desired position within the tubular 130, pressurized fluid is injected into the piston through fluid port 320. The fluid actuates the piston 370, which forces the slips 340 towards the wedge lock assembly 350. The wedge lock assembly 350 functions to bias the slips 340 outwardly as the slips are slidably forced along the outer surface of the assembly, thereby forcing the slips to engage the inner wall of the tubular 130.
FIG. 4 illustrates a cross-sectional view of a top drive 200 engaged to a tubular 130. The figure shows slips 340 engaged with the inner wall of the tubular 130 and a spring 360 in the decompressed state. In the event of a hydraulic fluid failure, the springs 360 can bias the piston 370 to keep the slips 340 in the engaged position, thereby providing an additional safety feature to prevent inadvertent release of the tubular string 210. Once the slips 340 are engaged with the tubular 130, the top drive 200 can be raised along with the cylindrical body 300. By raising the body 300, the wedge lock assembly 350 will further bias the slips 340. With the tubular 130 engaged by the top drive 200, the top drive can be relocated to align and thread the tubular with tubular string 210.
In another embodiment (not shown), a top drive 200 includes a gripping means for engaging a tubular on the outer surface. For example, the slips can be arranged to grip on the outer surface of the tubular, preferably gripping under the collar 380 of the tubular 130. In operation, the top drive is positioned over the desired tubular. The slips are then lowered by the top drive to engage the collar 380 of the tubular 130. Once the slips are positioned beneath the collar 380, the piston is actuated to cause the slips to grip the outer surface of the tubular 130. Sensors may be placed in the slips to ensure proper engagement of the tubular.
FIG. 5 is a flow chart illustrating a typical operation of a string or casing assembly using a top drive and a spider. The flow chart relates to the operation of an apparatus generally illustrated in FIG. 1B. At a first step 500, a tubular string 210 is retained in a closed spider 400 and is thereby prevented from moving in a downward direction. At step 510, top drive 200 is moved to engage a tubular 130 from a stack with the aid of an elevator 120. The tubular 130 may be a single tubular or could typically be made up of three tubulars threaded together to form a stack. Engagement of the tubular by the top drive includes grasping the tubular and engaging the inner surface thereof. At step 520, the top drive 200 moves the tubular 130 into position above the tubular string 210. At step 530, the top drive 200 threads the tubular 130 to tubular string 210. At step 540, the spider 400 is opened and disengages the tubular string 210. At step 550, the top drive 200 lowers the tubular string 210, including tubular 130 through the opened spider 400. At step 560 and the spider 400 is closed around the tubular string 210. At step 570 the top drive 200 disengages the tubular string and can proceed to add another tubular 130 to the tubular string 210 as in step 510. The above-described steps may be utilized in running drill string in a drilling operation or in running casing to reinforce the wellbore or for assembling strings to place wellbore components in the wellbore. The steps may also be reversed in order to disassemble the casing or tubular string.
Although the top drive is a good alternative to the Kelly and rotary table, the possibility of inadvertently dropping a tubular string into the wellbore exists. As noted above, a top drive and spider must work in tandem, that is, at least one of them must engage the tubular string at any given time during tubular assembly. Typically, an operator located on the platform controls the top drive and the spider with manually operated levers that control fluid power to the slips that cause the top drive and spider to retain a tubular string. At any given time, an operator can inadvertently drop the tubular string by moving the wrong lever. Conventional interlocking systems have been developed and used with elevator/spider systems to address this problem, but there remains a need for a workable interlock system usable with a top drive/spider system such as the one described herein.
There is a need therefore, for an interlock system for use with a top drive and spider to prevent inadvertent release of a tubular string. There is a further need for an interlock system to prevent the inadvertent dropping of a tubular or tubular string into a wellbore. There is also a need for an interlock system that prevents a spider or a top drive from disengaging a tubular string until the other component has engaged the tubular.
The present invention generally provides an apparatus and methods to prevent inadvertent release of a tubular or tubular string. In one aspect, the apparatus and methods disclosed herein ensure that either the top drive or the spider is engaged to the tubular before the other component is disengaged from the tubular. The interlock system is utilized with a spider and a top drive during assembly of a tubular string.